The invention relates to a fuel injection nozzle for internal combustion engines with a closing spring preloading the position of a needle valve, the tension on which is varied by an adjustment mechanism arranged to shift a spring support, which mechanism is accessible exteriorly of the injection nozzle and is operable through rotation thereof.
In a known fuel injection nozzle, an adjusting screw with a counter nut, disposed in the axis of the nozzle in a nozzle holder, serves as rotatable means with said adjusting screw arranged to move a cap supported on a spring. Since one side of the fuel injection nozzle is required for connection with a fuel line, it was not possible hitherto in known fuel injection nozzles to either align or change the closing force of the spring without completely disassembling the nozzle. Such a change in the tension of the locking spring becomes necessary as a result of a gradual fatigue of the spring or as a result of adaptation of a particular fuel injection nozzle to different engines requiring varying opening pressures of the injection nozzle. It also should be noted that the diameters of the fuel injection nozzles are relatively small, as a result of the requirements of the producers of the internal combustion engines and that such an apparatus for the change of the pre-load tension of the locking spring is exposed to extraordinarily strong forces, requiring a correspondingly sturdy construction.